Bullet seating depth.

[Vloc1987]

I have a some confusion about bullet seating depth I hope I can get cleared up. For the most part I understand about measuring to the Ogive and backing off from the lands. When I measured with hornady chamber gauge my .308 with hornady 150 gr fmj and it my initial measurement to the lands was 2.251 with the ogive of the bullet. So then I backed off the lands .020 so then I made the bullet 2.231 that I get I believe. The part that confuses me is that I checked to see what the OAL was just to see where I was at and I was longer than the 2.810 which is the basic OAL given in the load book I use for reloading. Does that measurement not matter as much now that I am measuring to the ogive and as long as the bullets seat in the magazine? I know this is a lot to take in but I just don’t want to seat the bullet too far out.
Thanks for any advice!

 

[Kaldor]

What is your COAL at 20 thou off?

Likely the chamber on your rifle is deeper than the COAL listed in the book. Happens alot on factory guns. On my Savage 308 with a Criterion Im running at like 2.90 COAL with Berger 180s.

 

[Vloc1987]

What is your COAL at 20 thou off?

Likely the chamber on your rifle is deeper than the COAL listed in the book. Happens alot on factory guns. On my Savage 308 with a Criterion Im running at like 2.90 COAL with Berger 180s.

With my bullet seated .020 off the lands at 2.231 the OAL measurement is 2.818. I just was confused about sammi spec and the 2.810 listed in the book. For OAL. If that was the max I had to be at or since I measured off the lands then that wouldn’t matter. I know most all the different loads for 308 in the book were all over the place for OAL from 2.603- 2.800 depending on which bullet was used. None of them went above 2.800 though so I was just making sure I was okay to be over it.

 

[CptnAwesome]

What I've found typically is that the suggested COAL is quite a bit (not sure the number) shorter than what you'll find is .020" off the lands in factory rifles. This applies to every factory rifles I've loaded for.

Edit: So I don't pay any attention to suggested COAL if I've determined my max CBTO. From there I just determine how far off the lands I want to be and measure CBTO when determining seating depth.

 

[Vloc1987]

What I've found typically is that the suggested COAL is quite a bit (not sure the number) shorter than what you'll find is .020" off the lands in factory rifles. This applies to every factory rifles I've loaded for.

Edit: So I don't pay any attention to suggested COAL if I've determined my max CBTO. From there I just determine how far off the lands I want to be and measure CBTO when determining seating depth.

Thank you. I took a precision reloading class which explained this and I just took it in thinking I didn’t have a question about it. And going through measuring my chamber I just checked the OAL just for ****s and giggles and noticed it was bigger and i had a huge brain fart and it made me overthink it wayyy too much.

 

[CptnAwesome]

Thank you. I took a precision reloading class which explained this and I just took it in thinking I didn’t have a question about it. And going through measuring my chamber I just checked the OAL just for ***** and giggles and noticed it was bigger and i had a huge brain fart and it made me overthink it wayyy too much.

When it comes to reloading, pretty sure it's way better to overthink than underthink...

 

[Bfh_auto]

With my bullet seated .020 off the lands at 2.231 the OAL measurement is 2.818. I just was confused about sammi spec and the 2.810 listed in the book. For OAL. If that was the max I had to be at or since I measured off the lands then that wouldn’t matter. I know most all the different loads for 308 in the book were all over the place for OAL from 2.603- 2.800 depending on which bullet was used. None of them went above 2.800 though so I was just making sure I was okay to be over it.

If you are working up a load. The book values are reference points.
Our overall length varies by chamber or magazine length.
Our max powder charge varies by cartridge overall length and distance to the rifling.
Look at it like driving a car. The speed limit is 55. Sometimes you can't drive 55 because of environmental factors. We all know someone who goes over the speed limit. A little won't get you in trouble most of the time. But doing it recklessly can get you in serious trouble.

 

[Blue68f100]

You only have a problem when the round will not fit the magazine if your using one. Other wise you what ever OAL you want. A 0.020" jump is a good starting point. But you may find that most ELD type bullets like long jumps, or say more forgiving. I have a few rounds that don't fit the magazine, I use a bobsled to single feed them.

 

[Howa 9700]

I'm somewhat new to this too, and have similar questions and concerns. Putting this out there for clarification and to set me straight if I'm wrong, but as I understand COAL as relates to SAMMI specs, as long as a bullet is seated to SAMMI specs (between min and max)......it should feed from any magazine, then chamber and fire in any gun chambered for that round. Yet depending on the gun, it may not be the best fit for an individual gun (for best accuracy), and best fit to lands or bullet jump for some bolt guns can be greater than max COAL. So bullets are seated for that gun, and that gun only. As long as it feeds, chambers and fires, it's OK.

But there also seems to be a minimum seating depth.....there needs to be enough grip on the bullet by the case neck. Seems min seating depth was somewhere around bullet diameter? So even if you could seat forward of that (say with a lighter, shorter bullet) you shouldn't?

 

[mdi]

If;
You know your handloads won't jam the bullets in the rifling,
You know your handloads will fit the magazine,
You know your handloads are safely loaded,
Just "ignore" book OAL and consider your handloads "custom" and assembled for your particular gun...

I believe SAAMI specs are "industry standards" designed/tested to work in all production firearms safely, and not hard and fast "laws"...

Edit 5/3;
"SAAMI was founded in 1926 at the request of the federal government and tasked with creating and publishing industry standards for safety, interchangeability, reliability and quality, coordinating technical data and promoting safe and responsible firearms use."

 

[AJC1]

Sammi is the saftey net for basic loading that should eliminate any safety conserns and provide flawless functionality in any weapon. If you are loading custom ammunition the expectation is that you understand the hows and whys of pressure and the impacts of the decisions you make outside the saftey nets of sammi. Single loaded rounds can easily exceed sammi spec because magizne limitations dont matter. Your decreasing pressure until you contact the lands. If your going long you may also end up exceeding powder charges listed in the book to hit a node or get book speed. The saftey in all of this is knowing what is happening and what to expect.

 

[FROGO207]

The OAL listed is what they used for the particular set of components in that particular firearm that resulted in a safe load. Changing any one of them (firearm) changes your results. This is given as a safe starting point to use their data in making your custom loads, nothing more. AJC1 Beat me to it.

 

[Bfh_auto]

I'm somewhat new to this too, and have similar questions and concerns. Putting this out there for clarification and to set me straight if I'm wrong, but as I understand COAL as relates to SAMMI specs, as long as a bullet is seated to SAMMI specs (between min and max)......it should feed from any magazine, then chamber and fire in any gun chambered for that round. Yet depending on the gun, it may not be the best fit for an individual gun (for best accuracy), and best fit to lands or bullet jump for some bolt guns can be greater than max COAL. So bullets are seated for that gun, and that gun only. As long as it feeds, chambers and fires, it's OK.

But there also seems to be a minimum seating depth.....there needs to be enough grip on the bullet by the case neck. Seems min seating depth was somewhere around bullet diameter? So even if you could seat forward of that (say with a lighter, shorter bullet) you shouldn't?

That's spot on.
Good job typing all that up without rambling or missing anything.